A glomerulus is organized by epithelial cells, mesangial cells, endothelial cells, and epithelial cells of Bowman's capsule. The glomerulus filtrates blood to produce a glomerular filtrate containing substantially the same components as plasma components of which molecular weight is 10,000 or less. Generally, the filtration is controlled not to leak essential substances in blood, especially serum protein, to urine.
Glomerulus damage causes the growth of mesangial cells which are one of the glomerulus component cells and the expansion of a neighbor extracellular matrix to increase the amount of urinary protein excretion. It is known that the increase of urinary protein excretion further lowers the renal function by leading glomerulopathy to damage of renal tubules. Therefore, the inhibition of the urinary protein excretion is expected to improve various diseases associated with glomerulopathy. Such damage is derived from not only a primary disease but also a systemic disease such as diabetes. However, initiation and progression mechanisms remain uncertain and a fundamental method for treatment is not established.
As the present treating method, symptomatic therapies are carried out, but they have many problems. For example, the immunosuppressants are used for patients of nephritis because many types of nephritis are considered to be caused by immunologic mechanism, but nephrotoxicity occurs by the prolonged administration. Though steroids are also administered to the patients of nephritis, some nephritis are resistant to them. Recently, it is proved that angiotensin converting enzyme inhibitors (antihypertensive agents) are useful for nephritis. However, the medicament for nephritis without a hypotensive effect is required.
Accordingly, pharmacotherapy of glomerulopathy has been in a trial and error stage. The treatment of glomerulopathy is made more difficult by the fact that the cause of glomerulopathy is not all alike and clinical course full of variety can not easily be prospected.
As a treating agent for nephritis other than the above mentioned medicament, compounds described in JP-A-9-87176 are exemplified.
Compounds similar to those of the present invention are described in WO97/27174, EP0757984 A1, EP0757037 A2, WO97/45402, WO97/44315, WO96/00214, WO95/35276, and WO97/05865.